This sample demonstrates the difference between undef a and a = undef.
Example reftest4.bas :
b = 12
ref a = b
ref b = a
' this does not brake the reference, but assigns undef to b (and a)
b = undef
print a," = undef\n"
' Set b to be 12
b = 12
' a becomes the same as b
ref a = b
' b is already the same as a
ref b = a
' b is undefed, but a retains the value
undef b
print a," = 12\n"
undef a
Result executing reftest4.bas :
Possible error messages sent to stderr: